Technical Field
The present disclosure relates to an infusion pump for feeding medicinal solution and the like to a patient. Particularly, the present disclosure relates to the infusion pump in which an infusion tube is attached to the infusion pump in a horizontal direction to feed liquid.
Background Art
An infusion pump is used in, for example, an intensive care unit (ICU) or the like, and applied to feed medicinal solution to a patient for a relatively long period with high accuracy. A predetermined medicinal solution bag (infusion bag) is disposed above the infusion pump. An infusion tube hung from the medicinal solution bag is sandwiched between a main body and an access door, and the infusion tube is housed inside the main body and held by closing the access door. Inside the main body of the infusion pump, an outer peripheral surface of the infusion tube set at a predetermined position is sandwiched between a plurality of fingers inside the main body and an inner surface of the access door. A peristaltic infusion pump is configured to feed the medicinal solution by sequentially pressing the outer peripheral surface of the infusion tube with the plurality of fingers along a length direction by individually driving the plurality of fingers of a liquid feed driving unit (e.g., refer to JP 2010-200775 A).
According to the infusion pump disclosed in JP 2010-200775 A, the infusion tube is held being vertically passed through the inside of the main body of the infusion pump from above downward. In contrast, there is a proposed infusion pump in which an infusion tube is held being horizontally passed through the inside of a main body of the infusion pump. A reason for adopting such a configuration in which the infusion tube is held being horizontally passed through the inside of the main body of the infusion pump is so that the infusion tube is not obstructive even when a plurality of infusion pumps is held in a state vertically stacked. This is different from the infusion pump in which the infusion tube is vertically passed through the inside of the main body of the infusion pump from above downward. For example, an upstream side of the infusion tube is set at a right-side portion when a person faces the main body of the infusion pump and a downstream side of the infusion tube is set at a left-side portion when a person faces the main body of the infusion pump. In this case, the medicinal solution can be fed from the upstream side to the downstream side in a predetermined feeding direction and can be correctly fed to a patient by driving the liquid feed driving unit when the upstream side of the infusion tube is set at the right-side portion of the main body of the infusion pump and the downstream side of the infusion tube is set at the left-side portion of the main body of the infusion pump.
An infusion pump includes a bubble detection unit (bubble sensor) configured to detect whether a bubble exists inside the infusion tube. The bubble sensor includes an ultrasonic transmitting unit and an ultrasonic receiving unit. In a type of the infusion pump where an infusion tube is held being vertically passed through the inside of a main body of the infusion pump, when a boundary between medicinal solution and air (bubble) passes a portion where a flow path of the infusion tube is narrowed at the bubble sensor, the medicinal solution directly flows downward in a state such that the liquid surface of the medicinal solution is spread over an entire part of the portion where the flow path of the infusion tube is narrowed.
In contrast, in a type of the infusion pump where the infusion tube is held being horizontally passed through the inside of a main body of the infusion pump, when the boundary between the medicinal solution and the air (bubble) passes the portion where the flow path of the infusion tube is narrowed at the bubble sensor, the medicinal solution (also referred to as droplet of the medicinal solution) is partly caught at an inner surface of the portion where the flow path of the infusion tube is narrowed, and the medicinal solution may partly remain inside the portion where the flow path of the infusion tube is narrowed because of influences from surface tension of the medicinal solution and gravity.
When the medicinal solution thus partly remains inside the portion where the flow path of the infusion tube is narrowed, ultrasonic from the ultrasonic transmitting unit of the bubble sensor is transmitted through a part of the remaining medicinal solution and received by the ultrasonic receiving unit. Due to this, the bubble sensor may determine that the medicinal solution exists inside the infusion tube and erroneously detects that there is no bubble although the bubble actually exists inside the infusion tube.